RFC documents moved to rfc directory; Added more RFC documents
Fixed appendSig caused GPG signature invalid bug
This is because
  1. sig_file may contains local end of line (\n) instead of canonical end of line (\r\n)
  2. appendSig append "<BR>\n" to HTML mail, which is also a local(*NIX) end of line

修正了附加个性签名时导致 GPG 电子签名无效的问题
原因：
  1. 个性签名文件可能包含本地系统所的回车换行符(例如：\n)，而不是正规回车换行符(\r\n)
  2. appendSig 把 "<BR>\n" 附加到了 HTML 邮件中，\n 也不是正规回车换行符号